A method for manufacturing a heat source

ABSTRACT

The invention relates to a method for the manufacturing of a combustible heat source ( 1 ) for an aerosol forming article, comprising: —Providing a mould ( 100 ) defining a cavity ( 101 ) having a first opening ( 102 ); —Providing a chamber ( 106 ) above said cavity ( 101 ), the chamber ( 106 ) having a second opening ( 108 ) fluidly connected to the first opening ( 102 ); —Placing a particulate component ( 104 ) in the chamber ( 106 ); —compressing the particulate component ( 104 ) in the chamber ( 106 ) up to a first pressure so that it forcedly flows into said cavity ( 101 ); and —compressing the particulate component ( 104 ) in the cavity ( 101 ) up to a second pressure higher than said first pressure to form the combustible heat source ( 1 ).

The present invention relates to a method of manufacturing a heat source.

A number of aerosol forming articles in which tobacco is heated rather than combusted have been proposed in the art. One aim of such ‘heated’ aerosol forming articles is to reduce known harmful smoke constituents of the type produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes. In one known type of heated aerosol forming article, an aerosol is generated by the transfer of heat from a combustible heat source to an aerosol forming substrate located downstream of the combustible carbonaceous heat source. During smoking, volatile compounds are released from the aerosol forming substrate by heat transfer from the combustible heat source and entrained in air drawn through the aerosol forming article. As the released compounds cool, they condense to form an aerosol that is inhaled by the user.

For example, WO-A2-2009/022232 discloses a smoking article comprising a combustible heat source, an aerosol-forming substrate downstream of the combustible heat source, and a heat-conducting element around and in direct contact with a rear portion of the combustible heat source and an adjacent front portion of the aerosol-forming substrate.

Combustible heat sources for use in such aerosol forming articles are known to be manufactured in multi-stage process in which the heat source is formed by pressing particulate material to form a solid heat source. The particulate material is known to be carbon-based and non-carbon-based, and may also comprise a binder to improve the structural properties of the heat source. The heat conducting element is then attached to the heat source in a subsequent process.

As such, it is an object of the present invention to provide a method of manufacture that increases the efficiency of manufacturing combustible heat sources.

The invention relates to a method for the manufacturing of a heat source for an aerosol forming article. The method comprises providing a mould defining a cavity having a first opening; providing a chamber above said cavity, the chamber having a second opening fluidly connected to the first opening; placing a particulate component in the chamber; compressing the particulate component in the chamber up to a first pressure so that it forcedly flows into said cavity; and compressing the particulate component in the cavity up to a second pressure higher than said first pressure to form the heat source.

Providing such a method, advantageously, minimizes the number of wasted particulate component and heat sources. Further, heat sources can be fabricated faster than with other methods due to the rejection rate reduction.

Preferably, said heat source is a combustible heat source.

Preferably, said particulate component includes a carbonaceous material.

As used herein, the term ‘carbonaceous’ is used to describe heat sources and particulate components comprising carbon.

In embodiments where the particulate component is carbonaceous, the first particulate component preferably has a carbon content of at least about 35 percent, more preferably of at least about 45 percent, most preferably of at least about 55 percent by dry weight of the first particulate component. In certain preferred embodiments, the first particulate component preferably has a carbon content of at least about 65 percent by dry weight of the first particulate component.

Particulate components for use in methods according to the invention for making combustible carbonaceous heat sources may comprise one or more additives in order to improve the properties of the combustible carbonaceous heat source. Suitable additives include, but are not limited to, additives to promote consolidation of the combustible carbonaceous heat source (for example, sintering aids), additives to promote ignition of the combustible carbonaceous heat source (for example, oxidisers such as perchlorates, chlorates, nitrates, peroxides, permanganates, zirconium and combinations thereof), additives to promote combustion of the combustible carbonaceous heat source (for example, potassium and potassium salts, such as potassium citrate) and additives to promote decomposition of one or more gases produced by combustion of the combustible carbonaceous heat source (for example catalysts, such as CuO, Fe₂O₃ and Al₂O₃).

Where methods according to the invention are used to make combustible carbonaceous heat sources for aerosol forming articles, at least one of the particulate components comprises carbon. Preferably, at least one of the particulate components comprises an ignition aid. In certain embodiments, at least one of the particulate components may comprise carbon and an ignition aid.

In embodiments where the first particulate component comprises an ignition aid, the first particulate component preferably has an ignition aid content of less than or equal to about 60 percent, more preferably of less than or equal to about 50 percent, most preferably of less than or equal to about 40 percent by dry weight. In certain preferred embodiments, the first particulate component preferably has an ignition aid content of less than or equal to about 30 percent by dry weight.

As used herein, the term ‘ignition aid’ is used to denote a material that releases one or both of energy and oxygen during ignition of the combustible heat source, where the rate of release of one or both of energy and oxygen by the material is not ambient oxygen diffusion limited. In other words, the rate of release of one or both of energy and oxygen by the material during ignition of the combustible heat source is largely independent of the rate at which ambient oxygen can reach the material. As used herein, the term ‘ignition aid’ is also used to denote an elemental metal that releases energy during ignition of the combustible heat source, wherein the ignition temperature of the elemental metal is below about 500° C. and the heat of combustion of the elemental metal is at least about 5 kJ/g.

As used herein, the term ‘ignition aid’ does not include alkali metal salts of carboxylic acids (such as alkali metal citrate salts, alkali metal acetate salts and alkali metal succinate salts), alkali metal halide salts (such as alkali metal chloride salts), alkali metal carbonate salts or alkali metal phosphate salts, which are believed to modify carbon combustion. Even when present in a large amount relative to the total weight of the combustible heat source, such alkali metal burn salts do not release enough energy during ignition of a combustible heat source to produce an acceptable aerosol during early puffs.

Examples of suitable oxidizing agents include, but are not limited to: nitrates such as, for example, potassium nitrate, calcium nitrate, strontium nitrate, sodium nitrate, barium nitrate, lithium nitrate, aluminium nitrate and iron nitrate; nitrites; other organic and inorganic nitro compounds; chlorates such as, for example, sodium chlorate and potassium chlorate; perchlorates such as, for example, sodium perchlorate; chlorites; bromates such as, for example, sodium bromate and potassium bromate; perbromates; bromites; borates such as, for example, sodium borate and potassium borate; ferrates such as, for example, barium ferrate; ferrites; manganates such as, for example, potassium manganate; permanganates such as, for example, potassium permanganate; organic peroxides such as, for example, benzoyl peroxide and acetone peroxide; inorganic peroxides such as, for example, hydrogen peroxide, strontium peroxide, magnesium peroxide, calcium peroxide, barium peroxide, zinc peroxide and lithium peroxide; superoxides such as, for example, potassium superoxide and sodium superoxide; iodates; periodates; iodites; sulphates; sulfites; other sulfoxides; phosphates; phospinates; phosphites; and phosphanites.

As used herein, the term ‘particulate component’ is used to describe any flowable particulate material or combination of particulate materials including, but not limited to, powders and granules. Particulate component used in methods according to the invention may comprise two or more particulate materials of different types. The particulate components used in methods according to the invention may comprise two or more particulate materials of different composition.

The particulate component is used to realize a heat source. In order to realize such a source, the particulate component is pressed using a forming press or mould which comprises a specific cavity into which the particulate component is inserted by means of a first opening, and where it is then transformed to adequate volume, shape and density by the application of pressure, up to a second pressure value, to create the desired heat source.

Before reaching the cavity, the particulate component is first put into a chamber, for example a tank, which can be located above or in proximity of the cavity of the forming press or mould and is in fluid communication to the same. The fluid connection between the chamber and the cavity may be realized for example forming a second opening in the chamber and connecting it to the first opening of the cavity.

Thus, an amount of the particulate component need to be freed from the chamber and inserted into the cavity, where a cavity pressure up to the second pressure is to be applied. However, if the particulate component transfer from the chamber to the cavity takes place only due to gravity, for example by sliding, several problems may arise.

The second pressure applied to the particulate component to compress it into a heat source has a predetermined value and this value is preferably reached with rather high accuracy due the fact that if the heat source has a too high density, for example due by the application of a too high second pressure, the gasses generated during the combustion of the heat source may have difficulties in being expelled from the particulate, which may create internal stress that could break the heat source into parts which could fall from the aerosol generating article.

A problem occurs when the gravity force is not sufficient to make the right amount of particulate component fall into the cavity, resulting in its partial filling. When the specified second pressure is therefore applied to a partially filled cavity, the resulting heat source is to be rejected, causing a waste of particulate component and production time.

The cause of this problem could be that the mechanical fluidity of the particulate component, partly determined by granulometry distribution and moist of the particulate, is too low relatively to the cavity diameter. However, both these quantities, cavity diameter and mechanical fluidity of the particulate component, cannot be easily changed.

Because the cavity diameters are determined according to market accepted diameters of the aerosol generating article, and used by numerous other machineries implied in the manufacturing process, these diameters could not be adjusted to fit what could be mechanically needed for the particulate component.

Furthermore, the density of the particulate component cannot be changed without modifying its composition, which has been determined and fixed with great care to optimize its heat release.

According to the invention, in order to solve the above stated problems, an additional pressure is applied to the particulate component when the particulate is still in the chamber and not yet in the cavity. This pressure, which reaches a first pressure value, “forces” the particulate to fall from the chamber to the cavity. In this way, the correct amount of particulate component is likely present in the cavity.

Preferably, when the correct amount of particulate component has fallen into the cavity, the chamber is moved aside, leaving just the particulate component which is in the cavity and saving other particulate that has been poured into the chamber for next uses. This step can be performed before or after the application of the cavity pressure up to a second pressure.

Due to the application of a pressure up to the first pressure, the mechanical fluidity of the particulate component is not an obstacle any more for the correct filling of the cavity. Adapting the chamber pressure up to the first pressure to the mechanical fluidity of the particulate component allows to obtain the desired cavity filling with any particulate component and in a variety of external conditions, for example in presence of higher or lower moisture which may alter the fluidity of the particulate component. The value of the first pressure can be substantially freely varied, contrary to the value of the second pressure which is substantially fixed, as explained above. However, in this free variation, the first pressure does not equal or exceed the second pressure, because the application of a pressure inside the chamber up to the first pressure is preferably not compacting the particulate component in a single dense object, as the application of the second pressure does, but still allows the particles forming the particulate component to move independently or in small clusters to avoid obstructions of the cavity first opening.

Further, the application of a pressure up to the first pressure in the chamber allows a quick flow of particulate component into the cavity, speeding up the manufacturing process.

After the application of the pressure in the chamber up to the first pressure, a pressure in the cavity up to the second pressure is applied to the particulate component in the cavity to compact the same. The value of the second pressure is unchanged by the presence of the application of a pressure up to the first pressure, therefore it can be optimized for achieving the correct density of the heat source, for example for the proper gas release during combustion.

The resulting compacted particulate is then optionally ejected out of the cavity, and processed to become a heat source.

Preferably, the method of the invention, between the phase of compressing the particulate component at a chamber pressure up to a first pressure and the phase of compressing the particulate component at a cavity pressure up to a second pressure, includes a step during which no pressure is applied, with the exception of atmospheric pressure, to said particulate component for a predetermined time. The particulate component according to the method of the invention is preferably not subjected to a continuously increasing pressure. Preferably the particulate is subjected to two separate steps in which different pressures, up to the first pressure and up to the second pressure, respectively, are applied for a given amount of time. Between the application of a pressure up to the first pressure and the application of a pressure up to the second pressure, preferably no pressure with the exception of atmospheric pressure is applied for a given time interval. For example, the pressure application can be as follows. The pressure in the chamber up to the first pressure pushes the particulate component into the cavity. The chamber is then preferably shifted from the cavity and during this shift there is an interruption in the pressure application: no pressure is applied to the particulate with the exception of the standard atmospheric pressure. Then, the cavity pressure up to the second pressure is applied, and the particulate component is compacted into a heat source by this pressure.

The two pressure steps could be one subsequent to the other, without a time interval in between. Preferably, the step of compressing said particulate component in the cavity up to the second pressure takes place only when the step of compressing the particulate component in the chamber up to the first pressure is terminated.

The chamber pressure up to the first pressure can be applied in a plurality of different ways, all encompassed by the present invention. The method preferably comprises providing a fluid flow in the chamber to push said particulate component towards said cavity. The fluid flow acting on the particulate component provides the pressure up to the first pressure. This pressure can be optionally regulated changing the flow rate of the fluid. More preferably, the fluid flow includes an air flow. Air is a cheap and easy-to-control fluid and therefore it is preferably used in the present method.

When this fluid flow is applied, preferably the method comprises the step of fluid-tightening the chamber to the mould. In this way, the fluid flow can build up a pressure higher than the atmospheric pressure and up to the first pressure in the chamber. When the chamber is shifted from the cavity, the fluid-tightening is removed and the pressure in the chamber and in the cavity may return back to the atmospheric pressure.

Advantageously, a piping is provided connecting the chamber to a fluid reservoir. In order to obtain a fluid flow to push the particulate towards the cavity, the chamber is preferably connected to a fluid reservoir, for example an air reservoir, where the fluid is contained. Preferably, a fan or blower, for example located within the flow reservoir, is imparting to the fluid the necessary speed and flow rate towards the particulate component.

The chamber pressure up to the first pressure may be imparted by means of a first mechanical pressing device to compress said particulate component towards the cavity. Mechanical pressing device and air flow can also coexist imparting both a pressure, the sum of which generates a total pressure up to the first pressure, to the particulate component so that it flows in the right amount to the cavity. The mechanical pressing device could include a movable wall, for example a wall of the chamber, which moves the particulate component towards the second opening. Said mechanical pressing device may include a piston having a downwards movement. If a mechanical pressing device is used to apply the pressure up to the first pressure in the chamber to the particulate component, preferably a sensor of the applied chamber pressure is also present in the chamber, to generate for example feedback signals further used to optionally increase, decrease or stop the exerted pressure in the chamber.

Preferably, the method comprises the step of sensing a weight of particulate component present inside the cavity. More preferably, the method also includes the step of interrupting the compression inside said chamber when said weight of particulate component in the cavity is above a cavity set threshold. The amount of particulate inside the cavity is preferably well controlled in order to obtain a heat source of the desired size and density. In order to check that the correct amount of particulate component has been pushed, by means of the chamber pressure up to the first pressure, inside the cavity, a sensor to check the amount of the particulate is included in the cavity. The sensor determines the weight of the particulate component fallen in the cavity and, preferably, if a certain threshold is reached, called cavity set threshold, sends a signal to interrupt the first pressure in the chamber. The weight of the particulate component inside the cavity can be displayed visually and an operator may manually interrupts the chamber pressure application.

Preferably, the method of the invention includes the step of tuning the applied pressure during the compression step inside the chamber. In this way, the pressure in the chamber can be varied, always up to the first pressure, for example with reference to the amount of particulate component present in the cavity. The pressure variations in the chamber can have predetermined patterns. More preferably, the variation of the pressure in the chamber includes slowly increasing a pressure during the compression step inside said chamber till the weight of the particulate material inside said cavity reaches a set threshold.

Preferably, the method of the invention includes the step of tuning the applied pressure during the compression step inside the cavity. The pressure in the chamber or in the cavity may be tuned in such a way that it is applied in different subsequent sub-steps, for example in a number of sub-steps equal to N. In each sub-step of the sequence, the pressure reaches a maximum value, the maximum pressure value of each sub-step being preferably equal to or lower than the maximum pressure value of the subsequent sub-step. This means that the pressure in the cavity raises up to the second pressure in N sub-steps, and in each j-sub-step with j=1, . . . , N the maximum reached pressure is equal to P_(j) with P_(j)≤P_(j+1) and where P_(N)=second pressure.

Preferably, in the method of the invention, the pressure in the cavity up to the second pressure is applied in a plurality of N sub-steps. Even more preferably, the pressure up to the second pressure is applied in N≤five sub-steps. Preferably, the sub-steps are equal to N=three. Tuning the pressure applied in the cavity, as in the case of applying the pressure in different sub-steps, allows having a more homogeneous density inside the heat source.

The first pressure is preferably optimized to push the particulate component inside the cavity and at the same time to avoid compacting it excessively, avoiding clogging. Preferably, said first pressure is comprised between about 0.005 MegaPascal (5′10³ N/m²) and about 0.5 MegaPascal (5*10⁵ N/m²). The second pressure is preferably optimized to obtain a heat source having the proper density and dimensions. Preferably, said second pressure is comprised between about 1 MegaPascal (10⁶ N/m²) and about 50 MegaPascal (5*10⁷ N/m²). Preferably, a pressure equal to the first pressure or equal to the second pressure is applied for a time interval comprised between about 0.01 seconds and about 2 seconds. Preferably, the first pressure is comprised between about 0.02 MegaPascal and about 0.1 MegaPascal. More preferably, the pressure equal to the first pressure is applied for a time interval equal to about 0.1 seconds to about 0.5 seconds, even more preferably for about 0.15 seconds. Preferably, the second pressure is comprised between about 5 MegaPascal and about 20 MegaPascal. More preferably, the pressure equal to the second pressure is applied for a time interval equal to about 0.1 seconds to about 1 second, even more preferably for a time interval equal to about 0.2 seconds to about 0.4 seconds.

More preferably, the pressure in the cavity up to the second pressure is applied in N sub-steps, one subsequent to the other. Preferably, N 5 five sub-steps. Preferably, each sub-steps lasts between about 0.2 seconds and about 0.3 seconds. In each sub-step, a maximum pressure is defined called P. If the number of sub-steps is N=3, the maximum pressure of each j-sub-step, where j=1, 2, 3, is preferably equal to: P₁ which has a value ranging from about 1 MegaPascal to about 3 MegaPascal; P₂ which has a value ranging from about 4 MegaPascal to about 8 MegaPascal and P₃ which has a value ranging from about 10 is MegaPascal to about 12 MegaPascal. Preferably, a pressure equal to P₁ is applied in the cavity for a time interval comprised between about 0.2 and about 0.3 seconds, then a pressure equal to P₂ is applied in the cavity for a time interval comprised between about 0.2 and about 0.3 seconds and then a pressure equal to P₃=second pressure is applied in the cavity for a time interval comprised between about 0.2 and about 0.3 seconds.

The ratio between the first pressure and the second pressure is preferably comprised between about 0.0001 and about 0.5, more preferably between about 0.0017 and about 0.1.

Advantageously, the method of the invention further comprises providing a hopper fluidly connected to the chamber; placing the particulate component in the hopper; and moving by gravity the particulate component from the hopper to the chamber. In order to minimize the consumption and the waste of particulate component, the particulate component is introduced in a hopper from where it is then released to slide, due to gravity, via for example a pipe, to the chamber in small controlled amounts. Advantageously, the diameter of the pipe could be adjusted, if needed, to make sure that every kind of particulate component is apt to fall easily from the hopper to the chamber by means of gravity only. In this way, in the chamber, only a relatively small amount of particulate component is present and only such a small amount has to be moved by the chamber pressure application.

When a proper amount of particulate component is present into the chamber, preferably the method includes the step of sealing the chamber to the mould when an amount of particulate component in the chamber reaches a chamber set threshold. Sealing the chamber to the mould assures that a proper control of the pressure applied into the chamber is achieved.

Preferably, the method includes the step of moving away the chamber from above the cavity when the step of compressing the particulate component in the chamber up to a first pressure has ended. In this way, the step of refilling the chamber with new particulate component and the compressing step with a pressure up to the second pressure in the cavity can be performed in parallel reducing production time. In addition, between the application of the chamber pressure up to the first pressure and the application of the cavity pressure up to the second pressure, only atmospheric pressure acts onto the particulate component.

It is to be understood that, although a single cavity has been mentioned, the mould might include a plurality of cavities. The chamber may include a plurality of apertures so as to be in fluid communication with each cavity. In each cavity of the mould, a pressure up to the second pressure is applied and the particulate component herein present is compressed so as to obtain a heat source. The plurality of cavities may be provided in a single row, or in multiple rows or staggered rows.

The pressure up to the second pressure inside the cavity can be applied by second mechanical means, such as a piston. In case of a plurality of cavities, then, for each cavity, one piston comes down—preferably vertically—into the cavity, applying pressure to the particulate component into the cavity so that it acquires a determined density and shape.

Preferably, the method further comprises ejecting the formed combustible heat source from the cavity. The formed heat source is preferably ejected by moving the piston out of the mould.

The portion of the mould defining the cavity walls may move downwards, and the portion of the mould defining the base of the cavity may remain stationary relative to the portion defining the cavity walls. Preferably, the ejection of the heat source from the mould cavity corresponds to the chamber slidably advancing across the mould, such that an external face of the chamber removes the heat source from the work area.

The method may comprise utilising a continuously rotating multi-cavity press, a so-called turret press. The cavities may rotate about a central axis. The particulate component is provided in the cavity from a chamber, the chamber being stationary relative to the cavity receiving the particulate component. As such, the chamber reciprocates along a line defined by an arc. The piston is provided vertically above the cavity, and during the step of applying the second pressure, the piston is stationary relative to the cavity to which the pressure is applied. As such, the piston reciprocates both vertically, and along a line defined by an arc. The formed combustible heat source is then ejected from the mould.

As described further below, the combustible heat source may be blind or non-blind. As used herein, the term ‘blind’ is used to describe a combustible heat source in which air, drawn through an aerosol forming article comprising the heat source, for inhalation by a user does not pass through any airflow channels along the combustible heat source.

As used herein, the term ‘non-blind’ is used to describe a heat source in which air, drawn through a smoking article comprising the heat source, for inhalation by a user passes through one or more airflow channels along the combustible heat source.

The heat source may comprise a plurality of layers. The layers are preferably formed from different particulate material such that distinct layers are formed having distinct properties. The plurality of layers may be formed by placing a first particulate material in the mould cavity, and placing a second particulate material in the mould cavity. The first particulate material corresponds to the first layer and the second particulate material corresponds to the second layer. The first particulate material is pushed in the cavity by means of a pressure up to the first pressure. The second particulate material is also pushed into the cavity by a pressure applied in the chamber up to a first pressure. The two operations can be performed in series.

Preferably, combustible heat sources made by methods according to the invention have an apparent density of between about 0.8 g/cm³ and about 1.1 g/cm³, more preferably about 0.9 g/cm³.

Preferably, combustible heat sources made by methods according to the invention have a length of between about 2 mm and about 20 mm, more preferably of between about 3 mm and about 15 mm, most preferably of between about 9 mm and about 11 mm.

Preferably, combustible heat sources made by methods according to the invention have a diameter of between about 5 mm and about 10 mm, more preferably of between about 7 mm and about 8 mm, most preferably about 7.8 mm in diameter.

Preferably, combustible heat sources made by methods according to the invention are of substantially uniform diameter. However, methods according to the invention may be used to make combustible heat sources that are tapered such that the diameter of a first end of the combustible heat source is greater than the diameter of an opposed second end thereof.

Preferably, combustible heat sources made by methods according to the invention are substantially cylindrical. For example, methods according to the invention may be used to make cylindrical combustible heat sources of substantially circular cross-section or of substantially elliptical cross-section.

As used herein, the term ‘length’ is used to describe the dimension in the longitudinal direction of smoking articles.

The combustible heat source as described herein may be used in aerosol forming articles. The aerosol forming article may comprise a combustible heat source, an aerosol forming substrate, a transfer section such as an expansion chamber, a filter section and a mouthpiece. The combustible heat source is preferably provided at a first end of the aerosol forming article adjacent the aerosol forming substrate. The barrier of the combustible heat source is provided between the heat source and the aerosol-forming substrate. The mouthpiece is provided at a second end of the aerosol forming article.

As used herein, the term “aerosol forming substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol. An aerosol forming article is an article comprising an aerosol forming substrate that is capable of releasing volatile compounds that can form an aerosol. An aerosol forming article may be a non-combustible aerosol forming article or may be a combustible aerosol forming article. Non-combustible aerosol generating article releases volatile compounds without the combustion of the aerosol forming substrate, for example by heating the aerosol forming substrate, or by a chemical reaction, or by mechanical stimulus of an aerosol forming substrate. Combustible aerosol forming article releases an aerosol by direct combustion of an aerosol forming substrate, for example as in a conventional cigarette.

The aerosol forming substrate is capable of releasing volatile compounds that can form an aerosol and may be released by heating or combusting the aerosol forming substrate.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

FIGS. 1a-1d show schematic diagrams of steps of the method to produce a heat source according to the invention; and

FIGS. 2a and 2b show a top view and a lateral view of a heat source realized according to the method of the invention.

FIGS. 1a, 1b, 1c and 1 d show schematic representations of steps for the manufacture of a heat source according to the present invention and globally indicated with 1. The realized heat source 1 at the end of the method of the invention is depicted in an enlarged view in FIGS. 2a and 2 b.

The machinery 10 utilised to manufacture the heat source 1 is arranged as follows. A mould 100 is provided that defines the side walls of a cavity 101 for forming the heat source 1. The top wall of the cavity is open defining a first opening 102. The mould side walls and the bottom wall may be movable relative to each other in order to change the size of the cavity. The cavity 101 is cylindrical.

A hopper 103 is provided that is configured to hold and release particulate matter 104 via an hopper outlet 105. Further, the machinery 10 includes a chamber 106 which is fluidly connected to the hopper 103 by means of a pipe 107. The chamber 106 is slidably mounted relative to the mould 100, such that it can reciprocate along a line perpendicular to the longitudinal axis of the cavity 102. Further, chamber 106 is positioned on top of the mould 100 and includes a second opening 108. Preferably, the dimension of the second opening is equal to or bigger than that of the first opening 102.

A piston 109 is provided vertically above the cavity 102 and is arranged such that the longitudinal axis of the piston and the longitudinal axis of the cavity 101 are aligned. Preferably, the piston 109 has a compressive area, that is the area that enters into contact to the particulate during the application of a pressure onto the particulate, of about 0.5 square centimetres. Optionally a second piston (not depicted in the drawings) including a bottom wall of the cavity is also slidable and arranged such that the longitudinal axis of the second piston and the longitudinal axis of the cavity 101 are aligned. Piston 109 and second piston may cooperate to compress material present in the cavity therebetween.

Further, a fluid reservoir 110 is fluidly connected to the chamber 106 by means of pipe 111. Preferably pipe 111 branches off pipe 107. Fluid reservoir 110 preferably includes a fan or blower 112 to blow the fluid towards the chamber 106.

The chamber 106 could be air-sealed to the forming mould 100, except for the pipes 107/111. For instance, the chamber could have all around its bottom a compressible seal (not visible in the drawings) and the chamber could be mechanically pressed on the mould 100, making it air-sealed, except for the pipes.

A weight sensor 113 can be provided inside cavity 101 to weight the particulate material introduced therein. The weight sensor 113 may send signals relating to the weight of the particulate material to a control unit 114 apt to command fan or blower 112 and to increase, decrease or interrupt the air flow in the chamber 106 as a function of the particulate material weight. The connection between control unit 114, fan or blower 112 and sensor 113 is depicted as dashed lines in the FIGS. 1a -1 b.

FIG. 1a shows the chamber 106 positioned above the mould 100 such that the first and second openings 102, 108 are located one on top of the other. In this position, the hopper 103 is filled with particulate material 104 and therein stored. The hopper 103 provides the chamber 106 with particulate material 104 via pipe 107 along the direction of arrows 20. Sufficient particulate material is provided into the chamber 106 to form a single heat source 1. The flow of the particulate material takes place by gravity.

Then chamber 106 is air-tighten to mould 100.

After the particulate material 104 has reached the chamber 106 from the hopper 103, FIG. 1b shows the activation of the fan or blower 112 so that a flow of air is introduced in the chamber 106 by means of pipe 117 along the direction of the arrow 30. Fan or blower can be activated by means of a command sent by control unit 114. In this way, due to the air-tight connection between chamber and mould, a pressure is built up in chamber 106 and the particulate material 104 present in the chamber 106 moves into the cavity 101 being pushed by the air blow. The pressure built up in the chamber is controlled, for example by means of suitable sensors (not depicted) so that it does not exceed the first pressure. Preferably, the air pressure applied is comprised between about 0.02 MegaPascal and about 0.1 MegaPascal for about 0.15 seconds so that the particulate component enters the chamber. Weight sensor 113 may send signals to the control unit 114 which, depending on the weight of the particulate material 104 introduced in the cavity, may vary the pressure exerted by the air flow. When the desired weight is achieved, control unit 114 stops the air flow and thus no more pressure in addition to the atmospheric pressure is present in the chamber 106. The control unit in order to interrupt the application of the chamber pressure may for example send a switch off signal to the fan 112.

FIG. 1c shows the chamber 106 retreating from the cavity filling position shown in FIGS. 1a and 1b . As the chamber 106 slides away from the mould cavity opening 102, the piston 109 advances towards the cavity 101, in the direction as shown by arrow 40. Therefore, the particulate material 104 present in the cavity 101 is compressed by the piston 109 which presses the particulate towards the walls of the cavity 101. The piston 109 compresses particulate material 104 till a second pressure is reached which is pre-determined. The second pressure is high enough to pack together the particulate material which then is substantially “glued” together to form a single unit.

Preferably, the second pressure is reached in three different subsequent sub-steps. The piston 109 moves down towards the bottom of the cavity and starts compressing the particulate in a first sub-step, applying a force of between about 0.05 kiloNewton to about 0.15 kiloNewton for a time interval comprised between about 0.2 seconds to 0.3 s seconds. The piston 109 then proceeds further compressing the particulate in a second sub-step with a strength of between about 0.2 kiloNewton to about 0.4 kiloNewton for a time interval comprised between about 0.2 seconds to about 0.3 seconds. In the third sub-step, the piston compresses the particulate in the cavity even more, with strength of between about 0.5 kiloNewton to about 0.6 kiloNewton, which defines the second pressure value, for a time interval comprised between about 0.2 seconds to about 0.3 seconds. FIG. 1d shows the piston 109 retreated from the cavity 101. As the piston 109 retreats, the mould portion defining the walls of the cavity is preferably lowered relative to the portion of the mould forming the bottom of the cavity. In this way, the heat source 1 is ejected from the mould cavity. As the mould portion defining the side walls of the cavity is lowered, the chamber 106 is slidably advanced along the top face of the mould to begin the process of manufacturing a further heat source. As the chamber advances, the leading edge of the chamber 106 is utilised to clear the formed heat source from the work area. In this way, a continuous process is provided.

FIGS. 2a and 2b show the formed heat source 1. The compressed particulate material forms the heat source. The heat source is approximately about 7.8 mm in diameter and approximately about 9 mm in length. As shown in FIG. 2b the combustible heat source 1 is substantially circular in cross-section.

The heat source is used in an aerosol forming device. The article comprises a heat source formed as described above, an aerosol forming substrate provided adjacent the barrier of the heat source, a diffuser, a transfer section, a filter adapted to condense vapour, and a mouthpiece filter. As the user draws on the aerosol forming article, air is drawn through ventilation holes upstream of the aerosol-forming substrate which entrains the aerosol.

The embodiments and examples described above illustrate but do not limit the invention. Other embodiments of the invention may be made without departing from the spirit and scope thereof, and it is to be understood that the specific embodiments described herein are not limiting. 

1. A method for the manufacturing of a heat source for an aerosol forming article, comprising: providing a mould defining a cavity having a first opening; providing a chamber above said cavity, the chamber having a second opening fluidly connected to the first opening; placing a particulate component in the chamber; compressing the particulate component in the chamber up to a first pressure so that it forcedly flows into said cavity; compressing the particulate component in the cavity up to a second pressure higher than said first pressure to form the heat source; and between the step of compressing the particulate component at a first pressure and the step of compressing the particulate at a second pressure, applying no pressure, with the exception of the atmospheric pressure, to the particulate component in the chamber for a predetermined time.
 2. A method for the manufacturing of a heat source for an aerosol forming article, comprising: providing a mould defining a cavity having a first opening; providing a chamber above said cavity, the chamber having a second opening fluidly connected to the first opening; placing a particulate component in the chamber; compressing the particulate component in the chamber up to a first pressure so that it forcedly flows into said cavity; compressing the particulate component in the cavity up to a second pressure higher than said first pressure to form the heat source; wherein said first pressure is comprised between about 0.005 MegaPascal and about 0.5 MegaPascal.
 3. A method for the manufacturing of a heat source for an aerosol forming article, comprising: providing a mould defining a cavity having a first opening; providing a chamber above said cavity, the chamber having a second opening fluidly connected to the first opening; placing a particulate component in the chamber; compressing the particulate component in the chamber up to a first pressure so that it forcedly flows into said cavity; compressing the particulate component in the cavity up to a second pressure higher than said first pressure to form the heat source; wherein the heat source has a length between 2 mm and 20 mm.
 4. The method according to claim 2, wherein, between the step of compressing the particulate component at a first pressure and the step of compressing the particulate at a second pressure, the method further comprises: Applying no pressure, with the exception of the atmospheric pressure, to the particulate component in the chamber for a predetermined time.
 5. The method according to claim 1, further comprising: Providing a fluid flow in said chamber to push said particulate component towards said cavity.
 6. The method according to claim 1, further comprising: Providing a first mechanical pressing device to compress the particulate component towards the cavity.
 7. The method according to claim 1, further comprising: Sensing a weight of particulate component present inside the cavity.
 8. The method according to claim 7, further comprising: Interrupting the compression inside the chamber when said weight of particulate component in said cavity is above a set threshold.
 11. The method according to claim 7, further comprising: Slowly increasing a pressure during the compression step inside said chamber till the weight of the particulate component inside said cavity reaches a cavity set threshold.
 12. The method according to claim 1, wherein said first pressure is comprised between about 0.005 MegaPascal and about 0.5 MegaPascal.
 13. The method according to claim 1, wherein the pressure equal to the first pressure is applied for a time interval comprised between about 0.01 seconds and about 2 seconds.
 14. The method according to claim 1, wherein said second pressure is comprised between about 1 MegaPascal and about 50 MegaPascal.
 15. The method according to claim 1, wherein the pressure equal to the second pressure is applied for a time interval comprised between about 0.01 seconds and about 2 seconds.
 16. The method according to claim 2, further comprising: Providing a fluid flow in said chamber to push said particulate component towards said cavity.
 17. The method according to claim 2, further comprising: Providing a first mechanical pressing device to compress the particulate component towards the cavity.
 18. The method according to claim 2, further comprising: Sensing a weight of particulate component present inside the cavity.
 19. The method according to claim 18, further comprising: Interrupting the compression inside the chamber when said weight of particulate component in said cavity is above a set threshold.
 20. The method according to claim 18, further comprising: Slowly increasing a pressure during the compression step inside said chamber till the weight of the particulate component inside said cavity reaches a cavity set threshold.
 21. The method according to claim 3, wherein, between the step of compressing the particulate component at a first pressure and the step of compressing the particulate at a second pressure, it includes: Applying no pressure, with the exception of the atmospheric pressure, to the particulate component in the chamber for a predetermined time.
 22. The method according to claim 3, wherein said first pressure is comprised between about 0.005 MegaPascal and about 0.5 MegaPascal.
 23. The method according to claim 3, further comprising: Providing a fluid flow in said chamber to push said particulate component towards said cavity.
 24. The method according to claim 3, further comprising: Providing a first mechanical pressing device to compress the particulate component towards the cavity.
 25. The method according to claim 3, further comprising: Sensing a weight of particulate component present inside the cavity.
 26. The method according to claim 25, including: Interrupting the compression inside the chamber when said weight of particulate component in said cavity is above a set threshold.
 27. The method according to claim 25, including: Slowly increasing a pressure during the compression step inside said chamber till the weight of the particulate component inside said cavity reaches a cavity set threshold. 